Liu Kuo-sung, an elder statesman of modern Chinese ink painting, is as modest as he is amiable. The 85-year-old’s paintings are considered reference points in the avant-garde progression from traditional formats of brush and ink, works that push boundaries to include both subjective influences from the modern world and self-invented painting techniques. As a solo painter and as one of the remaining members of the Fifth Moon Group, founded in Taiwan in 1956, his works are considered collectibles today, often sold by auction houses for tens of thousands of US dollars, with some achieving six-figure amounts.

We meet in Hong Kong, when his allocated hour-long interview at the city’s Art Basel event overruns by more than 30 minutes as he brightly delves into recollections from decades of painting and teaching. He has done both for some time: he is now chair professor at the National Taiwan Normal University (where he was a student), and served as a senior lecturer and head of the fine art department at the Chinese University of Hong Kong for two decades, from 1971.

It is a surprise to learn that his beginnings in art emerged from self-interest when his down-at-heel, widowed mother sent him from their home in Shandong, China to what he describes as something like an orphanage school in Taiwan. There, he spent hours on his own, drawing things around him. A watercolour self-portrait from when he was 17, in a thick retrospective book that Liu flips through during our conversation, clearly shows a tear trickling from a teenage eye to his mid-cheek. From around this age, he spent as many hours a day as he could painting, and studying techniques and styles that he saw in books about Western European artists of the early 20th century, before going to art school.

Liu is best known today for strong simple forms in ink and brush, some abstract, others based on a cosmic fascination. Celestial bodies that resemble Earth, Moon and Sun feature frequently – sometimes in relation to one another; at other times, a planet appears to be moving through a sequence of positions. Colours vary, from essentially black and white to colourful, with a play between texture: here a delicately mottled Earth or lunar surface, there a solid sprayed tomato-red solar sphere.

His first work to express a galactic fascination was Which Is Earth, painted in 1969 – after Liu had become somewhat obsessed with fresh images that were being taken of our planet from space by the 1968 Nasa Apollo 7 and 8 missions. This and subsequent monochromatic paintings launched a planet-focused period that followed a decade or so of abstract expressionist compositions, which had developed in rejection of his origins in traditional Chinese ink painting. “It was the first time many people had really had the chance to view our planet from so far away; I was so moved by these images,” Liu recalls. “I tried to see as many of these photos as possible and felt I had to try to bring some of this into my work.”

The solar system around our planet remains a passion with Liu today – as both an intellectual and an emotional curiosity. “Since the first time I saw these pictures, I found them so charming and mysterious,” he says. “And since that time, we have moved more and more into a new space age – landing on the Moon and Mars, discovering new planets and getting even better views of what Earth looks like. I’m still in love with this whole subject, and I’ve wanted to show what I feel about it.”

The moon in Liu’s paintings, though, has no relation to the name of the art collective to which he belonged through the 1960s. The Fifth Moon is a poetic-sounding yet simple translation of the Chinese phrase for the month of May, the fifth month of the year; the Taiwanese group’s name was inspired by the French Salon de Mai, a 1940s-founded modernist-art group.

Nature, a characteristic theme in Chinese inks, is also a constant in Liu’s oeuvre. A substantial body of work resulted after his visit to the mineral-coloured waters of the lakes in the mountains of Jiuzhaigou in Sichuan, in 2001. Like the views of earth from space, he says, the natural landscapes here “moved me emotionally”, and his drive to capture this was ignited, adding that he probably has not yet completed expressing his feelings on these landscapes through painting.

From 1959, Liu exhibited internationally, twice at Brazil’s São Paulo Biennial, at The Louvre in Paris as part of a 1985 group show, and at many more exhibitions afterwards.

While Liu and his Fifth Moon peers inspired generations of young ink painters to embrace worldly ideas within their work, does he feel there is much interest in the traditional form among young artists and art-appreciation circles in China and Taiwan today? “Older generations still paint in the old way – that’s how they were taught, and that’s how they think paintings have to be painted,” Liu says. “These days, though, younger people think that still painting like this is not very interesting. One reason I really like to teach is that I felt the old system is completely outdated. The traditional way is to copy old masters for many years, imitate them and then slowly develop your own style. I disagree with this – it keeps you in a box.

“My teaching style is: be different first, develop your own style and then perfect it later. Then the world is very open.”

Liu practices what he preaches: he’s spent decades trying to find the best way to achieve images that ferment in his mind. Some of his solutions have been techniques of his own invention. Attracted to the texture of stone rubbings popularly made through paper against stone carvings, one technique he experimented with was screwing up paper, dipping it in ink, then dabbing it onto a painting to transfer mottled ink onto an area.

“Chinese ink paintings use dot and line in black, Western also use planes and light,” he explained, “so I wanted to use [aspects of] both.”

To achieve these hybrid elements Liu also commissions his own paper, made with a top layer of pulp that has large flecks of thin bark; when the work is dry, he picks off the flecks, which leaves white marks across the surface.

In the 1970s, two other techniques that Liu began honing were marbling and what he calls “ink steeping”. Marbling involves a tank of water into which Liu introduces different coloured inks that float on its surface; he then swirls them into a configuration that he covers with a sheet of paper – this is peeled off carefully to reveal a print of the swish of inks. Ink steeping refers to two layers of paper – a water-soaked top sheet covers another (which can be wet or dry) that will be the finished work; the wet top sheet is painted upon, and ink then permeates to the base sheet. The results of marbling or ink steeping become a base Liu can work further into with brushes, scrunched paper balls and, more recently, an atomiser spray nozzle to deliver inky elements to complete the painting.

It is, in fact, the process of painting that influences Liu to create an image – rather than, say an earthly or cosmic landscape composition being rendered in one or more of his applications. “I have ideas that interest me, but let the process dictate the way a painting develops,” he says.

The orphan boy with an interest in art who took a leading role in modern Chinese ink painting is still very much on a mission. “I paint for six to eight hours a day,” he says. “Sometimes I paint abstract compositions and other times it’s natural forms – I don’t think I’ve finished with Jiuzhaigou or earth and planets in my work just yet. Painting is my life, and I simply go with what I feel at the moment.”